In the manufacture of complex printed circuit boards, hybrid thin film circuits, large scale integrated circuits and other circuit packs, it is necessary to run numerous manual tests using pairs of probes to ascertain the integrity of circuits paths and operability of circuit components. These tests are very tedious requiring exacting operator concentration and dexterity in manipulating and positioning the test probes. Due to the very close spacing of the circuit paths and terminals on components, eye contact between the test probe tips and the test sites is often lost when the operator looks up to read a meter or other monitor. This loss of eye contact often is accompanied by a slight shifting of one or both probes to engage other closely spaced circuit paths or terminal sites, thus resulting in improper circuit completions and false test readings.
Further, during sequential testing, the loss of eye contact with the test sites and the shifting of the test probes may interrupt the normal required testing sequence. In the testing of components having a large number of terminal sites to be tested, eye contact must be maintained in order that the test probes be sequentially moved from one site to the next test site without skipping a test site. It is thus apparent that there is a need for a test system which will permit an operator to maintain eye contact with test sites during a systematic sequential testing procedure.
In the prior art, various light emitting devices have been mounted on spectacles or eyeglass frames. Usually these devices have been used to provide a means for illuminating a viewing area. In one such device as shown in U.S. Pat. No. 4,086,004 issued Apr. 25, 1978, to Scrivo et al, one of a pair of spectacle bows is formed with a passageway for receiving a fiber-optic bundle that has an optically polished end positioned adjacent to one side of a lens. Light is impressed on the fiber-optic bundle to produce a light beam which impinges on an area in front of the lens.
Another spectacle mounted light emitting device is disclosed in U.S. Pat. No. 4,145,122 issued Mar. 20, 1978, to Rinard et al. In this instance, an infrared light source is mounted on the frame to project a light beam onto an infrared mirror surface of one lens, which beam is then reflected into the eye to form a virtual image behind the corneal surface of the eye. This image is reflected onto the mirror and then onto a detector which is also mounted on the spectacle frame. The detector functions to monitor movement of the eyeball.